uboot-phytec

pico-imx6ul, pico-imx7d: Enable USB and PXE boot support

This allow the use of a USB storage or PXE network booting as
fallback, allowing for example for manufacturing installation of eMMC
storage in an easy way.

Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>